Instrument for drawing ellipses



March 7, 1950 su 2,499,935

INSTRUMENT FOR DRAWING ELLIPSES Filed Dec. 4, 1945 Patented Mar. 7, 1950 UNITED STATES {PATENT OFFICE STRUMENT FOR DRAWING IELLIPSES .Paul A... Suto, Manchester, J.Conn., ,.,assignor., .to

O-ThruRuler Company, Hartford, Conn.

I Application December 4, 1945,:Serial'No; :632;652

. -7 Claims. 1 This inventionirelatesito' instruments for drawing ellipsesandmore particularly: to a drafting in- 'strumentiwhich. is adapted forzuse in accurately :drawing ellipses of different sizes.

A primary-object OffthlS'll'lVGIltiOl'l' is-to provide a simple ;and:.inexpensive instrument of sheet material having an :edgecthat is curved so. that .diiferentwp'ortions: thereof may be used in. draw- .ing ellipsest' for vdiiferent; diameters: thesaid instrument' being made. insets of differentI shapes, each to: produce. ellipses-of difierent sizes for certain angles of vision.

: Further objects andadvantages of this inven- .ztionr will be .imore 'clearly'understood from the sheets now commonly used.

The said instrument is formed intoamshape providing an edge 6 which is curved on gradually diminishing radiiforming a spiral terminating at a-point 1. The distance around said curved edge is graduated from zero to a: desirednumber of units-denoting inches of length of the major axis of ellipses for which the instrument may be used; the said" graduations running along the margin of the edgefi and each unit division thereof being sub-divided. into fractions as may be desired. It will benotedthat the graduations are numbered beginning at the point 7 and ending at the end '8. ofsaidedge B. 3 A line 9 isprovided opposite the said edge and graduated to conform with the graduations along the edge 6 for the purpose to be hereinafter described.

My improved instrument may be used for drawing ellipses of difierent sizes, as illustrated in Fig. 3 or" the drawings. The axes of the ellipse are first drawn, as shown, these axes consisting of a minor axis line H] and a major axis line H. The major axis of the ellipse which is to be drawn is then chosen on the graduations along the edge 6. As an example, in the illustration shown an ellipse is being drawn for a seven inch major axis. Therefore, the instrument is placed with the indicia along the edge 6 denoting seven inches upon the line 10 and aligned so that said line will cross the corresponding graduation on the line 9 with the said line i directly upon-the intersection .of the axis lines l0; and I i.- W'hen the-instrument isin this position, a quarter'oi, an ellipse maybedrawnby tracingaround the quartertoiigtheellipse-between the lines! I! and 1 H. and

within the :-portion; indicated by the arrows l2.

,Theqinstrmnenti is then turned to, the opposite edge. 6 otthenellipse, itheisaid quarter is then drawn; and- .thezinstrument maybe further turned for; drawing the remaining quartersofth'e ellipse.

After the four-quarters have. @beenpdrawn the ellipse .is..;complete..and the. major: axis of the ellipsei-will. be .in-izconformity IWith" the1 indicia 'which wasselected @fromthe graduation. alongthe curveof the edge 6.

It will. be :noted ,that the particular instrument illustrated inthedrawing hereof has indicia that is intended for. a-45 ellipse. ;.It is proposedthat the said instrument will be furnished in sets so that ellipses ior-- angles of sightmay be drawn.

In order to H indicate the corresponding I dimen- -sionsof the maor. and minor axes of an ellipse, 'for the"difierent angles-oi sight-,--each of saidinr struments is provided thereon with aline I 3 havi'ng correspondingscalesjuxtapositioned on oppo- 'site'sides thereof in'such a manner that any reading representing thelength of the major axis falls :opposite *areading representing the length of the minor axis'of the same ellipse. .It will be noted that the corresponding graduations on the edge 6 and line Q-extend perpendicularly to the cooperative portions thereof so that; when the different-quarters of an ellipse: .aredrawn; in the manner illustrated in Fig. 3, the linesdeiining thesaidquarters will merge and coincide; within a practical approximation, on.

.both the. minor and major axes.

Edge 6 is...an,. equi -angular spiral. plotted on .polar. coordinates. Consequently, proceeding from the point of origin, each successive portion of the curve is similar in curvature to all preceding portions but on an increasing scale; thus, once a portion of a spiral has been found to approximate a quarter segment of a given ellipse, different portions of the same spiral. will approximate to the same extent an infinite number of different sized ellipses of the same proportion as the first, within the arbitrary size limitations of a particular template. A series of templates of different curvatures are provided for drawing differently proportioned ellipses.

The locus of centers of all the ellipses that can be drawn with the same curve forms a similar 3 spiral, on line 9, having the same point of origin as the spiral of line 6.

Since the curvature of the spirals is mathematically constant, it is possible to apply a set of uniform graduations that tell the user precisely what portion of the curved edge to use for difierent sized ellipses, superimposing the proper graduations on any intermediate increments thereof upon the previously determined minor diameter of the required ellipse.

I claim:

1. An instrument for drawing ellipses comprising a sheet of transparent material having an edge in the form of a spiral, a line forming a spiral corresponding to the said edge, indicia running along the marginal portion of said edge and corresponding graduations along said edge and line providing a scale for indicating the position of said instrument for drawing ellipses of different sizes which are projections of different sized circles onto a single plane at an angle to the plane of the circles.

2. An instrument for drawing ellipses as set forth in claim 1 wherein the spiral line gradually converges towards the spiral edge to vary the position of the instrument for the drawing of ellipses of diminishing major and minor axis.

3. An instrument for drawing ellipses as set forth in claim 1 including a series or" lines running perpendicularly to the spiral edge for indicating the required positioning of the instrument with relation to an axis of the ellipse.

4. An instrument for drawing ellipses comprising a member constructed of a sheet of transparent material and having an edge in the shape of a spiral or gradually diminishing radii; the marginal portion of said spiral edge having measuring indicia for indicating the position of said edge relatively to the axis of an ellipse for drawing ellipses of different sizes, which are projections of different sized circles onto a single plane at an angle to the plane of the circles, a series of lines running perpendicular to said edge for indicating the position of the instrument with relation to an axis of the ellipse to be drawn, and a spiral line running opposite to said curved edge and gradually converging towards said edge, the said line being graduated for indicating the required position of the instrument relatively to the intersection of the major and minor axis of the ellipse.

5. An instrument for drawing ellipses which are projections of different sized circles onto a single plane at an angle to the plane of the circles, the said instrument comprising a sheet of transparent material having a curved edge in the form of a spiral; a line forming a correspond ing spiral and spaced from said edge and gradually converging in the direction thereof, and corresponding indicia on said line and along said edge for indicating the required position of said instrument relatively to an axis of an ellipse to be drawn therewith and to the intersection of major and minor axis of said ellipse.

6. An instrument for drawing ellipses which are projections of different sized circles onto a single plane at an angle to the plane of the circles, the said instrument comprising a fiat member of transparent sheet material having an edge thereof curved in the form of a spiral and to provide the curvature for quarters of ellipses of the same proportions of major to minor diameters, graduations running along the marginal portion of said curved edge, a line in the form of a spiral spaced from said edge and gradually converging therewith, and a series of corresponding graduations on said line and said edge providing means for positioning corresponded portions of said edge perpendicular to the minor and major axis lines drawn along said edge and defining separate quarters of the ellipse.

7. An instrument for drawing commercially practicable approximations of ellipses, said instrument comprising a member of transparent sheet material having as an edge thereof a first equi-angular spiral, graduations running along the marginal portion of said spiral edge to be placed at the extremities of the minor diameter of the required ellipse; a second equi-angular spiral having the same point of origin as the first spiral, and graduations on said line corresponding to graduations on the said edge to be placed on the intersection of the major and minor axes of the required ellipse for defining four symmetrical ninety degree segments of a series of ellipses of difierent sizes but of the same proportion of major to minor diameters.

PAUL A. SUTO.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date D. 138,016 Gilardi June 6, 1944 2,075,854 Karnes Apr. 6, 1937 2,245,915 I-Iartrampf June 17, 1941 2,247,362 Dibble July 1, 1941 FOREIGN PATENTS Number Country Date 358,902 Germany Sept. 19, 1922 565,908 Great Britain Dec. 4, 1944 OTHER REFERENCES Pages 139 and 142 of catalogue entitled Drafting and Reproduction Materials and Equipment Slide Rules, 39th edition, copyright 1943, published by Keuffel and Esser Co., 127 Fulton Street, New York, N. Y. (Copy in Design Division, U. S. Patent Oifice.) 

